Method for preparing cyclopeptide

ABSTRACT

A method for preparing a cyclopeptide, which includes the following steps: (A) providing compounds represented by the following formulas (II-1) or (II′-1) and (II-2); (B) performing a reaction between the compounds of formulas (II-1) or (II′-1) and (II-2), to obtain a compound represented by the following formula (II-3) and (II′-3), respectively; (C) performing a reaction between the compound of formula (II-3) or (II′-3) and a compound represented by the following formula (II-4) or (II′-4), respectively, is performed, to obtain a compound represented by the following formula (II-5), and (II′-5), respectively; (D) performing a cyclization reaction of the compound of formula (II-5) or (II′-5) with a catalyst of formula (III), to obtain a compound represented by the following formula (I) or (I′), respectively. The formulas (I), (I′), (II-1) to (II-5), (II′-1) to (II′-5) and (III) are shown in the specification.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application for“Cyclopeptide, pharmaceutical or cosmetic composition comprising thesame and method for preparing the same”, U.S. application Ser. No.15/488,550 filed Apr. 17, 2017, and the subject matter of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a cyclopeptide, a pharmaceutical orcosmetic composition comprising the same and a method for preparing thesame. More specifically, the present invention relates to a topical orcosmetic skin care cyclopeptide, a pharmaceutical or cosmeticcomposition comprising the same and a method for preparing the same.

2. Description of Related Art

Peptides have found widespread use in various fields, for example,topical or cosmetic skin care uses. Among the known peptides, thepeptide with arginine (R)-glycine (G)-aspartate (D) motif is found as acommon element in cellular recognition.

It is known that the peptide containing RGD motif can bind to theintergrin RGD binding site, and can be used to coat synthetic scaffoldsin tissue engineering to enhance cellular attachment by mimicking invivo conditions.

In the conventional method for preparing the peptide containing RGDmotif, coupling agents have to be used to catalyze the peptidesynthesis. However, the used amount of the coupling agents is not less,and the cost of the coupling agents itself is high. Hence, theproduction cost of the peptide is not low, and the obtained peptidecannot be available to all.

Therefore, it is desirable to provide a novel peptide containing RGDmotif and a novel method for preparing the peptide; so, the obtainedpeptide can be widely applied to various fields.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a novel cyclopeptideand a pharmaceutical or cosmetic composition comprising the same.

The RGD- and GRD-cyclopeptides of the present invention are respectivelyrepresented by the following formula (I) and (I′):

wherein,R₁ is

each of R₂ and R₃ independently is H or C₁₋₆ alkyl;X is O, S, CH₂ or N—R₄, in which R₄ is H, C₁₋₆ alkyl,(CH₂CH₂O)_(n)H—C(═O)—C₁₋₁₀ alkyl, or C(═O)(C₂H₄)₂C(═O)O(C₂H₄O)_(n)H, inwhich n=1-3.

Preferably, in the cyclopeptide of the present invention, R₃ is C₁₋₆alkyl when X is CH₂.

The pharmaceutical or cosmetic composition of the present inventioncomprises: an excipient; and the aforementioned cyclopeptide of thepresent invention.

In the cyclopeptide and the pharmaceutical or cosmetic composition ofthe present invention, X preferably is O, CH₂ or N—R₄, in which R₄ is H,C₁₋₆ alkyl, —C(═O)—C₄₋₁₀ alkyl, (CH₂CH₂O)_(n)H, orC(═O)(C₂H₄)₂C(═O)O(C₂H₄O)_(n)H, in which n=1-3.

In the cyclopeptide and the pharmaceutical or cosmetic composition ofthe present invention, R₁ preferably is

in which R₂ is H or C₁₋₆ alkyl, R₃ is C₁₋₆ alkyl; and R₄ is H,—C(═O)—C₄₋₁₀ alkyl or (CH₂CH₂O)_(n)H. More preferably, R₂ is i-propyl,R₃ is methyl when R₁ is

or R₄ is H or —C(═O)-heptyl when R₁ is

In one preferred aspect of the present invention, the cyclopeptides ofthe present invention are represented by any one of the followingformulas (I-1) to (I-5) and (I′-1) to (I′-5):

The cyclopeptide of the present invention comprises amino acids ofarginine (R), glycine (G) and aspartate (D), which can bind to theintergrin RGD binding site. When the cyclopeptide of the presentinvention binds to the intergrin RGD binding site of the skin, thecommunication process between dermis and epidermis can be revived, andthe production of important proteins of the basement membrane can bestimulated. Therefore, the purpose of ameliorating scars, wounds,inflammatory processes, aging and/or wrinkle formation can be achieved.Hence, the cyclopeptide and the pharmaceutical or cosmetic compositionof the present invention can be applied to topical or cosmetic skin carecomposition.

Preferably, in the cyclopeptide of the present invention, thecyclopeptide of the present invention is represented by any one of thecompounds of formulas (I-1) to (I-5) and (I′-1) to (I′-5). The productof the compound of formula (I′-5) after metabolism is ACHA(aminocyclohexane carboxylic acid) derivative, which is a non-naturalamino acid. However, for example, the product of the compound of formula(I′-3) is menthone, which is a natural molecule. Hence, compared tocompound of formula (I′-5), the compound of formulas (I′-1) to (I′-4) ispreferable.

In the pharmaceutical or cosmetic composition of the present invention,the suitable excipient for the present invention can be any excipientused in the art, for example, a binder, an anti-adhesive agent, adispersant and a lubricant.

Except for the aforementioned cyclopeptide and pharmaceutical orcosmetic composition of the present invention, another object of thepresent invention is to provide a novel bio-compatible, catalytic methodfor preparing the cyclopeptide of the present invention.

The method of the present invention comprises the following steps (A) to(D).

In the step (A), compounds represented by the following formulas (II-1)or (II′-1), and (II-2) are provided from commercial source or made byour catalytic methods.

R_(c)—NH—R₁—COOH  (II-2)

Herein, each of R_(a) and R_(b) independently is alkyl, cycloalkyl, arylor heteroaryl;

R_(c) is a protection group; and

R₁ is

in which each of R₂ and R₃ independently is H or C₁₋₆ alkyl; X is O, S,CH₂ or N—R₄, in which R₄ is H, C₁₋₆ alkyl, (CH₂CH₂O)_(n)H, —C(═O)—C₁₋₁₀alkyl, or C(═O)(C₂H₄)₂C(═O)O(C₂H₄O)_(n)H, in which n=1-3.

In the step (B), a reaction between the compounds of formulas (II-1) or(II′-1) and (II-2) is performed to obtain a compound represented by thefollowing formula (II-3) and (II′-3), respectively,

In the step (C), a reaction between the compound of formula (II-3) or(II′-3) and a compound represented by the following formula (II-4) or(II′-4), respectively, is performed to obtain a compound represented bythe following formula (II-5) and (II′-5), respectively.

wherein, each of R_(d) and R_(e) independently is a protection group.

In the step (D), a cyclization reaction of the compound of formula(II-5) or (II′-5) is performed with a catalyst of formula (III), toobtain a compound represented by the formula (I) or (I′), respectively.M(O)_(m)L¹ _(y)L² _(z)  (III)wherein M is a metal selected from the group consisting of IVB, VB, VIBand actinide groups;L¹ and L² respectively is a ligand;in and y are integers of greater than or equal to 1; andz is an integer of greater than or equal to zero.

In the method of the present invention, R_(c) and R_(d) can beFluorenylmethyloxycarbonyl (Fmoc); and R_(e) can be MTr(4-methoxy-2,3,6-trimethylbenzenesulphonyl). However, the presentinvention is not limited thereto.

In the method of the present invention, the reaction between thecompounds of formulas (II-1) or (II′-1) and (II-2) or the reactionbetween the compound of formula (II-3) and (II-4) or (II′-3) and (II′-4)can be performed with the catalyst of formula (III) or a coupling agent.

In the method of the present invention, when the reactions in the steps(B) to (D) are performed with the catalyst of formula (III), thecatalyst used in the steps (B) to (D) can be the same or different.

In the catalyst of formula (III), L¹ is a ligand, which preferably isselected from the group consisting of Cl, OTf, OTs, NTf₂, halogen,RC(O)CHC(O)R, OAc, OC(O)CF₃, OEt, O-iPr, and butyl, in which R is alkyl(preferably, C₁₋₆ alkyl; more preferably, C₁₋₃ alkyl). In addition, L²is also a ligand, which preferably is selected from the group consistingof Cl, H₂O, CH₃OH, EtOH, THF, CH₃CN and

Furthermore, in the catalyst of formula (III), M can be a metal selectedfrom the group consisting of IVB, VB, VIB and actinide groups. In oneaspect, M is a group IVB transition element, in is 1 and y is 2; whereinM can be Ti, Zr of Hf. In another aspect, M is a group VB transitionelement, in is 1 and y is 2 or 3; wherein M can be V or Nb. In anotheraspect, M is a group VIB transition element, in is 1 and y is 4; whereinM is Mo, W or Cr. In another aspect, M is a group VIB transitionelement, in is 2 and y is 2; wherein M is Mo, W or Cr. In furtheranother aspect, M is selected from the actinide group, in is 2 and y is2; wherein M is U. Specific examples for the catalyst of formula (III)can be MoO₂Cl₂, V(O)OCl₂, V(O)(OAc)₂, V(O)(O₂CCF₃)₂, Ti(O)(acac)₂,Zr(O)Cl₂, Hf(O)Cl₂, Nb(O)Cl₂, MoO₂(acac)₂, V(O)(OTs)₂, V(O)(NTf₂)₂, orVO(OTf)₂, but the present invention is not limited thereto.

Furthermore, in the catalyst of formula (III), z can be an integer ofgreater than or equal to zero; and preferably, z is 0.

In the conventional method for preparing the cyclopeptide, 3-5equivalent of coupling agents such as Hydroxybenzotriazole (HOBt),1-Hydroxy-7-azabenzotriazole (HOAt),2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate(HBTU) and benzotriazol-1-yl-oxytripyrrolidinophosphoniumhexafluorophosphate (PyBOP) are used. Because these coupling agents areexpensive, the obtained cyclopeptide cannot be easily commercialized andapplied to various fields.

In the method for preparing the cyclopeptide of the present invention,the catalyst of formula (III) is water soluble and used to facilitatethe reaction progress. Hence, the expensive coupling agents are not usedin the method of the present invention. Therefore, cyclopeptide can beproduced in a cheaper manner, and the obtained cyclopeptide can beapplied to various fields.

In the present invention, alkyl, cycloalkyl, aryl, and heteroarylpresent in the compounds include both substituted and unsubstitutedmoieties, unless specified otherwise. Possible substituents on alkyl,cycloalkyl, aryl, and heteroaryl include, but are not limited to, alkyl,alkenyl, halogen, alkoxy, ketone, alcohol, thioether, carbamate, amino,heterocyclic group or aryl; but alkyl cannot be substituted with alkyl.

In the present invention, the term “halogen” includes F, Cl, Br and I;and preferably is Cl or I. The term “alkyl” refers to linear andbranched alkyl; preferably, includes linear and branched C₁₋₂₀ alkyl;more preferably, includes linear and branched C₁₋₁₂ alkyl; and mostpreferably, includes linear and branched C₁₋₆ alkyl. Specific examplesof alkyl include, but are not limited to, methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, pentyl,neo-pentyl or hexyl. The term “alkoxy” refers to a moiety that the alkyldefined in the present invention coupled with an oxygen atom;preferably, includes linear and branched C₁₋₂₀ alkoxy; more preferably,includes linear and branched C₁₋₁₂ alkoxy; and most preferably, includeslinear and branched C₁₋₆ alkoxy. Specific examples of alkoxy include,but are not limited to, methoxy, ethoxy, n-propoxy, iso-propoxy,n-butoxy, iso-butoxy, sec-butoxy, tert-butoxy, pentyloxy, neo-pentyloxyor hexyloxy. The term “alkenyl” refers to a linear or branchedhydrocarbon moiety that contains at least one double bond; preferably,includes a linear and branched hydrocarbon C₂₋₂₀ moiety containing atleast one double bond; more preferably, includes a linear and branchedhydrocarbon C₂₋₁₂ moiety containing at least one double bond; and mostpreferably, includes a linear and branched hydrocarbon C₂₋₆ moietycontaining at least one double bond. Specific examples of alkenylinclude, but are not limited to, ethenyl, propenyl, allyl, or1,4-butadienyl. The term “aryl” refers to a monovalent 6-carbonmonocyclic, 10-carbon bicyclic, or 14-carbon tricyclic aromatic ringsystem. Specific examples of aryl include, but are not limited to,phenyl, naphthyl, pyrenyl, anthracenyl or phenanthryl; and preferably,the aryl is phenyl. The term “heterocyclic group” refers to a 5-8membered monocyclic, 8-12 membered bicyclic or 11-14 membered tricyclicheteroaryl or heterocycloalkyl having at least one heteroatom which isselected from the group consisting of O, S and N. Specific examples ofheterocyclic group include, but are not limited to, pyridyl,pyrimidinyl, furyl, thiazolyl, imidazolyl or thienyl.

Other objects, advantages, and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention has been described in an illustrative manner, andit is to be understood that the terminology used is intended to be inthe nature of description rather than of limitation. Many modificationsand variations of the present invention are possible in light of theabove teachings. Therefore, it is to be understood that within the scopeof the appended claims, the invention may be practiced otherwise than asspecifically described.

The cyclopeptide of one preferred embodiment of the present inventioncan be prepared as follows.

In Scheme I′ and II′, the coupling agents may also be used and can be,for example, Hydroxybenzotriazole (HOBt), 1-Hydroxy-7-azabenzotriazole(HOAt), 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate (HBTU) andbenzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate(PyBOP).

Hereinafter, the present invention provides examples for preparing thecyclopeptide of the present invention; but the present is not limitedthereto.

1-Amino-cis-4-methylcyclohexanecarboxylic Acid

4-Methylcyclohexanone (45 g., 0.4 mole), potassium cyanide (30 g., 0.4mole), and ammonium chloride (22.0 g., 0.4 mole) were dissolved in water(300 ml.) and alcohol (250 ml.) and kept at room temperature for 6 days.The dark solution was diluted with water (300 ml.) and saturated withhydrogen chloride. After a further 2 days1-amino-cis-4-methylcyclo-hexanenitrile hydrochloride (62-2 g, 88%) hadcrystallized. This hydrochloride (60 g.) was refluxed with 20%hydrochloric acid for 12 hr. The solution was evaporated to dryness, andthe residue extracted (Soxhlet) with ethanol-ether (9:1) for 8 hr. Afterremoval of the solvent, the residue was basified with aqueous ammonia,to yield 1-amino-cis-4-methylcyclohexanecarboxylic acid (45.5 g.),needles [from acetic acid-water (1:1)], m. p. 356-360′ (sublimes), R_(f)0.69 (Found: C, 61.6; H, 9.7; N, 8.4%. Calc. for C₈H₁₅NO₂: C, 61.1; H,9.6; N, 8.9%).

trans-2-Isopropyl-5-methylcyclohexane-1-spiro-5′-hydantoin

Prepared in 37% yield from natural (−)-menthone, this spiran formedneedles (from ethanol), m. p. 228-231.5° (Found: C, 63.0%; H, 8.8%; N,11.6%.)

1-Amino-trans-2-isopropyl-5-methylcyclohexanecarboxylic Acid

The previous hydantoin was hydrolysed by 60% sulphuric acid to theamino-acid, needles [from water-acetic acid (1:1)], m. p. 330° C.(Found: C, 66.0; H, 10.5; N, 6.8 for C₁₁H₂₁NO₂: requires C, 66.3; H,10.6; N, 7.0%).

Dipeptide Fmoc-Asp(O^(t)Bu)-D-Phe-OH Synthesis

To a solution of Fmoc-Asp(O^(t)Bu)-OH (2.06 g, 5 mmol, 1.0 eq) in1,2-dichloroethane (DCE, 10 mL) was added benzoic anhydride (1.14 g,5.05 mmol, 1.01 eq) and MoO₂Cl₂ (100 mg, 0.5 mmol, 10 mol %) at roomtemperature under N₂ atmosphere and the reaction was monitored by TLCanalysis. The reaction was stirred at room temperature for 2 h till thestarting amino acid was totally consumed and cooled to 0° C. A solutionof D-phenylalanine benzyl ester (1.275 g, 5.0 mmol, 1.0 eq) in 5 mL ofDCE was added to the above solution via syringe follow by the additionof amine base (5.0 mmol, 1.0 eq) at 0° C. The reaction mixture wasallowed stir at room temperature for 30 min. Solvent was evaporated, andthe remaining residue was dissolved in EtOAc (100 mL), washed withsaturated aqueous NaHCO₃ (30 mL), H₂O (30 mL), brine (30 mL), and driedover Na₂SO₄. After evaporation of solvent, the remaining residue waspurified by flash chromatography on silica gel to provideFmoc-Asp(O^(t)Bu)-D-Phe-OBn (2.68 g, 81% yield) as a white solid: TLCR_(f)=0.5 (EtOAc/Hexane=1/5); ¹H NMR (400 MHz, CDCl₃): δ 7.77 (d, J=7.6,2H), 7.57 (q, J=3.6, 2H), 7.41 (t, J=7.6, 2H), 7.35-7.32 (m, 4H),7.30-7.27 (m, 4H), 7.17 (t, J=6.0, 3H), 7.02 (t, J=6.4, 3H), 5.83 (br,1H), 5.13 (q, J=12.0, 2H), 4.87 (q, J=7.2, 1H), 4.58-4.49 (m, 1H), 4.36(d, J=7.2, 2H), 4.20 (t, J=7.2, 1H), 3.10 (dd, J=16.4, 5.6, 2H), 1.43(s, 9H); ¹³C NMR (100 MHz, CDCl₃) δ 170.8, 170.0, 156.0, 143.8, 143.6,141.3, 135.5, 135.0, 129.2, 128.6, 128.5, 127.7, 127.1, 125.1, 120.0,81.9, 67.3, 67.2, 53.4, 51.1, 47.0, 37.8, 37.3, 28.0; HRMS (ESI), Calcd.for C₄₀H₄₂N₂NaO₇ ([M+Na]⁺): 685.2889, found: 685.2887.

To a solution of Fmoc-Asp(O^(t)Bu)-D-Phe-OBn (2.0 g, 3.0 mmol, 1 equiv)in 150 mL of 1/1 (v/v) ratio of EtOAc/MeOH was added 10% Pd/C (383 mg,10 mol %) at RT. The reaction was allowed to stir in an atmosphere ofhydrogen (balloon) over 1.5 h, following which it was filtered overCelite. The Celite was washed multiple times with MeOH (30 mL), EtOAc(30 mL) and the combined filtrate was concentrated in vacuo to give1.699 g (99%) of dipeptide Fmoc-Asp(O^(t)Bu)-D-Phe-OH as a white solid.TLC R_(f)=0.23 (EtOAc/Hex=2/1)

¹H NMR (300 MHz, CDCl₃): δ 7.75 (d, J=7.5, 2H), 7.54 (d, J=7.2, 2H),7.39 (t, J=7.5, 2H), 7.29 (d, J=7.2, 2H), 7.23-7.16 (m, 5H), 7.06 (d,J=7.5, 1H), 6.12 (d, J=8.7, 1H), 3.21 (dd, J=9.6, 6.3, 1H), 3.06 (dd,J=9.6, 6.6, 1H), 2.72 (dd, J=16.8, 6.3, 1H), 2.57 (dd, J=16.2, 5.7, 1H),1.43 (s, 9H); ¹³C NMR (100 MHz, CDCl₃) δ 171.4, 170.8, 170.0, 156.0,143.7, 143.6, 141.2, 135.7, 129.2, 128.5, 127.7, 127.1, 125.1, 120.0,81.9, 67.3, 53.4, 52.3, 51.0, 47.0, 37.9, 37.4, 29.7, 28.0; HRMS (ESI),Calcd. for C₃₃H₃₆N₂NaO₇ ([M+Na]⁺): 595.2420, found: 595.2423.

Dipeptide Fmoc-Arg(Mtr)-Gly-OCH₃ Synthesis by EDC-HOBt Coupling

¹H NMR (400 MHz, CDCl₃): δ 7.72 (d, J=7.6, 2H), 7.63-7.54 (m, 3H), 7.25(t, J=7.6, 2H), 7.24-7.22 (m, 1H), 6.49 (br, 1H), 6.40 (br, 1H), 6.07(d, J=8.0 1H), 4.32 (q, J=6.8, 3H), 4.14 (t, J=7.2, 1H), 4.02 (dd,J=17.6, 5.2, 1H), 3.89 (dd, J=17.6, 5.2, 1H), 3.78 (s, 3H), 3.66 (s,3H), 3.34-3.23 (m, 2H), 2.66 (s, 3H), 2.60 (s, 3H), 2.16 (s, 3H), 2.05(s, 3H), 1.93 (t, J=6.0, 1H), 1.72-1.60 (m, 3H), 1.27 (t, J=6.8, 1H);¹³C NMR (100 MHz, CDCl₃) 172.8, 170.6, 158.6, 156.5, 143.8, 143.7,141.2, 138.5, 136.6, 134.7, 134.1, 133.0, 129.1, 127.7, 125.1, 124.9,124.3, 120.3, 120.0, 111.7, 67.1, 60.4, 55.4, 52.3, 47.0, 41.0, 40.2,31.9, 30.0, 29.7, 25.1, 24.0, 21.0, 18.3; HRMS (ESI), Calcd. forC₃₄H₄₁N₅NaO₈S ([M+Na]⁺): 702.2573, found: 702.2575.

Example 1

To a solution of Fmoc-Asp(O^(t)Bu)-D-Phe-OH (1.6 g, 2.8 mmol, 1.0 eq) in1,2-dichloroethane (DCE, 5 mL) was added 2,6-dinitrobenzoic anhydride(974 mg, 2.82 mmol, 1.01 eq) and MoO2Cl₂ (56 mg, 0.28 mmol, 10 mol %) atroom temperature and gradually heated 40° C. under N₂ atmosphere and thereaction was monitored by TLC analysis. The reaction was stirred at 40°C. for 2 h till the starting amino acid was totally consumed and cooledto 0° C. A solution of 1-aminocyclohexanecarboxylic acid benzyl ester(653 mg, 2.8 mmol) in 3 mL DCE was added to the above solution viasyringe follow by the addition of amine (2.8 mmol, 1.0 eq) at 0° C. Thereaction mixture was allowed stir at room temperature for 12 h. Solventwas evaporated, and the remaining residue was dissolved in EtOAc, washedwith saturated aqueous NaHCO₃ (1 mL), H₂O (1 mL), brine (1 mL), anddried over Na₂SO₄. After evaporation of solvent, the remaining residuewas purified by silica gel flash chromatography to provideFmoc-Asp(O^(t)Bu)-D-Phe-ACHA-OBn (1.69 g, 77% yield) as a white solid:TLC R_(f)=0.26 (EtOAc/Hexane=1/5); ¹H NMR (400 MHz, CDCl₃): δ 7.77 (d,J=7.6, 2H), 7.57 (d, J=7.2, 2H), 7.41 (t, J=7.6, 2H), 7.35-7.27 (m, 7H),7.24-7.16 (m, 5H), 6.95-7.89 (br, 1H), 6.21 (br, 1H), 5.72 (br, 1H),5.11 (q, J=8.0, 2H), 4.63 (q, J=7.6, 1H), 4.43-4.21 (m, 3H), 4.23 (t,J=7.2, 1H), 3.07 (dd, J=16.4, 6.4, 1H), 2.98-2.92 (m, 1H), 2.81 (dd,J=16.2, 4.8, 1H), 2.64-2.53 (m, 1H), 1.85-1.79 (m, 4H), 1.64-1.49 (m,3H), 1.47 (s, 9H), 1.26-1.20 (in, 4H); ¹³C NMR (100 MHz, CDCl₃) δ 173.5,170.8, 170.5, 169.6, 143.6, 141.3, 136.0, 129.4, 128.7, 128.5, 128.2,127.8, 127.1, 127.0, 125.0, 120.0, 82.0, 67.3, 66.8, 59.0, 54.1, 51.4,47.1, 37.3, 32.3, 32.1, 28.0, 24.9, 21.2, 18.3; HRMS (ESI), Calcd. forC₄₇H₅₃N₃NaO₈ ([M+Na]⁺): 810.3730, found: 810.3730.

To a solution of Fmoc-Asp(O^(t)Bu)-D-Phe-ACHA-OBn (1.5 g, 1.9 mmol, 1equiv) in 100 mL of 1/1(v/v) ratio of EtOAc/MeOH was added 10% Pd/C (242mg, 10 mol %) at RT. The reaction was allowed to stir in an atmosphereof hydrogen (balloon) over 2 h, following which it was filtered overCelite. The Celite was washed multiple times with MeOH (20 mL), EtOAc(20 mL) and the combined filtrate was concentrated in vacuo to give 1.31g (98%) of dipeptide Fmoc-Asp(O^(t)Bu)-D-Phe-ACHA-OH as a white solid:TLC R_(f) ⁼0.24 (EtOAc/Hex=2/1); ¹H NMR (400 MHz, CDCl₃): δ 7.75 (d,J=7.2, 2H), 7.73-7.72 (m, 6H), 7.40-7.32 (m, 5H), 7.31-7.21 (m, 6H),6.83 (d, J=16.0, 1H), 6.46 (d, J=5.4, 1H), 6.03 (br, 1H), 4.73 (q,J=7.6, 1H), 4.48-4.42 (m, 1H), 4.41-4.12 (m, 4H), 3.19-3.02 (m, 2H),2.84-2.68 (m, 2H), 2.18-1.65 (m, 6H), 1.49 (s, 9H), 1.63-1.24 (in, 10H);¹³C NMR (100 MHz, CDCl₃) δ 176.6, 171.6, 171.3, 171.1, 170.7, 156.2,143.7, 141.2, 136.6, 136.5, 129.3, 128.6, 127.7, 127.1, 126.9, 125.1,120.0, 81.7, 67.5, 59.4, 54.7, 52.1, 51.6, 47.0, 38.0, 37.3, 36.9, 36.7,32.9, 31.0, 29.7, 28.0, 25.0, 21.3, 21.1; HRMS (ESI), Calcd. forC₄₀H₄₇N₃NaO₈ ([M+Na]⁺): 720.3260, found: 720.3257.

A solution of H-D-Phe-Asp(OtBu)-OMe.HCl (1-HCl) (48.7 mg, 0.126 mmol,1.01 eq) in MeOH (1 mL) was cooled to 0° C., 1.5 eq NaHCO₃ was added andstirred for 0.5 h at rt. MeOH was evaporated and the resulting residualwas dissolved in 2 mL THF and dried with Na₂SO₄, and filtered. Thesolvent was removed and dried under vacuum to obtain D-Phe-Asp(OtBu)-OMe(1).

In a dry 50-mL, two-necked, round-bottomed flask was charged withMoO₂Cl₂ (5.0 mg, 0.025 mmol, 20 mol %) in anhydrous CH₂Cl₂ (1.0 mL). Tothe above solution, Fmoc-1-aminocyclohexane-1-carboxylic acid (2-1)(48.3 mg, 0.125 mmol) was added at ambient temperature followed byaddition of benzoic anhydride (29 mg, 0.127 mmol), and heated at 40° C.for 6 h then cooled to 0° C.

A solution of D-Phe-Asp(OtBu)-OMe (48.3 mg, 0.125 mmol) in DCM (0.5 mL)was added to above solution at 0° C. and gradually raise temperature tort and stir at rt for 2 h. Afterward 14 μL of 2,6-lutidine was added andcontinued stirred for additional 4 h at rt. The reaction was quenchedwith water (2 mL) and the organic phase was separated and the aqueousphase was extracted with dichloromethane (10 mL×2). The combined organicphase were dried over anhydrous Na₂SO₄ and concentrated. The crudeproduct was purified by column chromatography on silica gel (EA/Hex=2/3)and gave Fmoc-protected tripeptide (3′-1) (58 mg, 67%).

The procedure for preparing the tripeptide (3′) is not limited to theabove procedure, and Fmoc-protected tripeptide (3′-1) can be prepared,for example, by the following Scheme I′-2-1.

In a dry 25-mL, two-necked, round-bottomed flask was charged withcoupling reagent (1.0 equiv) in DCM (1 mL/mmol) and treated understirring with DIEA (3.0 equiv) at 0° C. for 5 min.Fmoc-1-aminocyclohexane-1-carboxylic acid (2-1) (182.7 mg, 0.5 mmol) wasadded at 0° C. for 10 min, and mixed with H-D-Phe-Asp(OtBu)-OMe.HCl (1)(192.7 mg, 0.55 mmol). The ice bath was removed after 10 min and thestirring continued at room temperature 96 h. The mixture was poured intoAcOEt (50× the DCM volume) and the solution treated according to theusual workup. The crude product was purified by column chromatography onsilica gel and gave Fmoc-protected tripeptide (3′-1). Yield: 68%

Purified by column chromatography (EtOAc/hexanes=3:7, R_(f)=0.2) ¹H NMR(400 MHz, CDCl₃) δ 7.74 (d, J=7.2 Hz, 2H), 7.57 (d, J=7.2 Hz, 2H),7.40-7.27 (m, 4H), 7.19-7.07 (m, 5H), 6.63 (d, J=8.0 Hz, 1H), 5.11 (s,1H), 4.84 (d, J=6.6 Hz, 1H), 4.74 (d, J=5.4 Hz, 1H), 4.41-4.32 (m, 2H),4.15 (t, J=6.4 Hz, 1H), 3.59 (s, 3H), 3.23 (dd, J=14.0, 6.9 Hz, 1H),3.04 (dd, J=14.0, 8.2 Hz, 1H), 2.76-2.63 (m, 2H), 1.92-1.77 (m, 2H),1.60-1.47 (m, 5H), 1.38 (s, 9H), 1.27-1.18 (m, 3H); ¹³C NMR (100 MHz,CDCl₃) δ 173.8, 171.2, 170.6, 169.2, 155.3, 143.6, 143.5, 141.1, 136.6,128.9, 128.3, 127.6, 126.9, 126.9, 124.8, 124.8, 119.8, 119.8, 81.3,66.7, 59.3, 53.5, 52.1, 48.7, 47.0, 37.2, 37.0, 32.4, 30.9, 27.7, 24.8,21.1, 21.0; HRMS (ESI) calcd for C₄₀H₄₇N₃O₈ (M+⁺Na): 720.3255; found:720.3253.

A solution of 200 mg (0.28 mmol) of the Fmoc-protected tripeptide (3′-1)was treated with 20% piperidine in DCM (1 mL) for 1 hour at roomtemperature. After removal of piperidine by coevaporation with methanol,the crude product was dried in vacuo and purified by columnchromatography on silica gel to obtain tripeptide (3-1).

Yield: 106.8/136.2=78%

Purified by column chromatography (EtOAc/hexanes=9:1, R_(f)=0.2) ¹H NMR(400 MHz, CDCl₃) δ 8.21 (d, J=8.2 Hz, 1H, NH), 7.21 (t, J=6.8 Hz, 2H),7.16-7.14 (m, 3H), 7.05 (d, J=8.4 Hz, 1H), 4.76-4.72 (m, 1H), 4.63-4.58(m, 1H), 3.66 (s, 3H, OCH₃), 3.15 (dd, J=14.0, 6.2 Hz, 1H), 3.00 (dd,J=14.0, 8.0 Hz, 1H), 2.81 (dd, J=16.0, 4.0 Hz, 1H), 2.51 (dd, J=16.0,4.0 Hz, 1H), 1.97-1.72 (m, 2H), 1.58-1.51 (m, 4H), 1.35 (s, 9H,C(CH₃)₃), 1.36-1.28 (m, 2H), 1.24-1.09 (m, 2H); ¹³C NMR (100 MHz, CDCl₃)δ 178.3, 170.9, 170.8, 169.9, 136.8, 129.1, 128.3, 126.6, 81.7, 57.1,53.8, 52.4, 48.2, 37.5, 37.1, 34.4, 34.1, 27.0, 25.0, 21.0; HRMS (ESI)calcd for C₂₅H₃₈N₃O₆ (M⁺+Na): 476.2755; found: 476.2753.

Example 2

In a dry 25-mL, two-necked, round-bottomed flask was charged withcoupling reagent (1.0 equiv) in DCM (1 mL/mmol) and treated understirring with DIEA (3.0 equiv) at 0° C. for 5 min.1-Boc-piperidine-4-Fmoc-amino-1-carboxylic acid (2-2) (233.27 mg, 0.5mmol) was added at 0° C. for 10 min, and mixed withH-D-Phe-Asp(OtBu)-OMe.HCl (1) (202.91 mg, 0.525 mmol). The ice bath wasremoved after 10 min and the stirring continued at room temperature 96h. The mixture was poured into AcOEt (50× the DCM volume) and thesolution treated according to the usual workup. The crude product waspurified by column chromatography on silica gel and gave Fmoc-protectedtripeptide (3′-2).

Yield: 259/399.17=65%

Purified by column chromatography (EtOAc/hexanes=3:7, R_(f)=0.2) ¹H NMR(400 MHz, CDCl₃) δ 7.75 (d, J=7.6 Hz, 2H), 7.56 (t, J=5.2 Hz, 2H), 7.39(dt, J=6.4, 2.4 Hz, 2H), 7.32-7.27 (m, 2H), 7.19 (t, J=7.6 Hz, 2H), 7.12(t, J=6.2 Hz, 3H), 6.68 (d, J=7.6 Hz, 1H), 4.79 (s, 1H), 4.44 (d, J=6.0Hz, 1H), 4.15 (t, J=6.2 Hz, 1H), 3.74-3.67 (m, 1H), 3.63 (s, 3H), 3.56(d, J=14.0 Hz, 1H), 3.19 (br, 1H), 2.99 (dd, J=14.0, 8.2 Hz, 1H), 2.89(br, 1H), 2.76 (dd, J=16.0, 6.0 Hz, 1H), 2.60 (d, J=12.8 Hz, 1H),2.05-1.96 (m, 1H), 1.77-1.53 (m, 6H), 1.42 (s, 9H), 1.38 (s, 9H); ¹³CNMR (100 MHz, CDCl₃) δ 172.7, 171.2, 170.5, 169.3, 155.3, 154.3, 143.5,143.4, 141.1, 136.5, 128.9, 128.3, 127.6, 126.9, 126.9, 126.7, 124.8,124.7, 119.8, 81.4, 79.6, 66.7, 57.6, 53.6, 52.3, 48.7, 46.9, 37.1,28.2, 27.8.

A solution of 219 mg (0.27 mmol) of the Fmoc-protected tripeptide (3′-2)was treated with 20% piperidine in DCM (1 mL) for 3 hour at roomtemperature. After removal of piperidine by coevaporation with methanol,the crude product was dried in vacuo and purified by columnchromatography on silica gel to obtain tripeptide (3-2).

Yield: 113/155.6=72%

Purified by column chromatography (EtOAc/hexanes=9:1, R_(f)=0.2) ¹H NMR(400 MHz, CDCl₃) δ 8.05 (d, J=8.2 Hz, 1H, NH), 7.26-7.14 (m, 5H), 7.05(d, J=8.4 Hz, 1H), 4.76-4.72 (m, 1H), 4.66-4.60 (m, 1H), 3.88-3.76 (m,2H, NH₂), 3.67 (s, 3H, OCH₃), 3.16 (dd, J=14.0, 6.2 Hz, 1H), 3.02-2.92(m, 3H), 2.82 (dd, J=17.0, 4.4 Hz, 1H), 2.52 (dd, J=17.0, 4.6 Hz, 1H),2.07-2.00 (m, 1H), 1.91-1.84 (m, 1H), 1.58-1.38 (m, 1H), 1.40 (s, 9H,C(CH₃)₃), 1.36 (s, 9H, C(CH₃)₃), 1.32-1.20 (m, 2H), 1.11-1.06 (m, 1H);¹³C NMR (100 MHz, CDCl₃) δ 176.7, 170.9, 170.6, 169.9, 154.4, 136.6,129.1, 128.4, 126.7, 81.7, 79.4, 55.3, 53.7, 52.4, 48.2, 37.5, 37.0,34.2, 28.2, 27.8; HRMS (ESI) calcd for C₂₉H₄₅N₄O₈ (M⁺+1): 577.3232;found: 577.3248.

Example 3 Scheme II Fmoc-Asp(O^(t)Bu)-D-Phe-ACHA-Arg(Mtr)-Gly-OCH₃Synthesis

To a solution of Fmoc-Asp(O^(t)Bu)-D-Phe-ACHA-OH (698 g, 1 mmol, 1.0 eq)in 1,2-dichloroethane (DCE, 5 mL) was added 2,6-dinitrobenzoic anhydride(348 mg, 1.01 mmol, 1.01 eq) and VO(OTf)₂ (55 mg, 0.15 mmol, 15 mol %)at room temperature and gradually heated 40° C. under N₂ atmosphere andthe reaction was monitored by TLC analysis. The reaction was stirred at40° C. for 4 h till the starting amino acid was totally consumed andcooled to 0° C. A solution of NH₂-Arg(Mtr)-Gly-OCH₃ (457 mg, 1 mmol) in3 mL DCE was added to the above solution via syringe follow by theaddition of base (1.0 mmol, 1.0 eq) at 0° C. The reaction mixture wasallowed stir at room temperature for 12 h. Solvent was evaporated, andthe remaining residue was dissolved in EtOAc (100 mL), washed withsaturated aqueous NaHCO₃ (20 mL), H₂O (20 mL), brine (20 mL), and driedover Na₂SO₄. After evaporation of solvent, the remaining residue waspurified by flash chromatography on silica gel to provideFmoc-Asp(O^(t)Bu)-D-Phe-ACHA-Arg(Mtr)-Gly-OCH₃ (612 mg, 68% yield) as awhite solid: TLC R_(f)=0.50 (EtOAc/Hexane=3/1); ¹H NMR (400 MHz, CDCl₃):δ 7.75 (d, 2H, J=7.20 Hz), 7.57 (m, 2H), 7.39 (t, 2H, J=7.6 Hz),7.30-7.18 (m, 7H), 6.60 (br, 1H), 6.55 (br, 1H), 4.67 (br, 1H),4.52-4.42 (m, 1H), 4.37 (q, 1H, J=6.40 Hz), 4.35-4.23 (m, 1H), 4.19 (t,1H, J=7.2 Hz), 4.14-4.04 (m, 1H), 3.81 (s, 3H), 3.69-3.61 (m, 1H), 3.58(s, 3H), 3.46-3.42 (m, 1H), 3.21-3.09 (m, 1H), 3.03-2.92 (m, 1H), 2.68(s, 3H), 2.59 (s, 3H), 2.25-2.11 (m, 1H), 2.10 (s, 3H), 2.04-1.83 (m,4H), 1.79-1.58 (m, 3H), 1.59-1.41 (m, 2H), 1.39 (s, 9H), 1.35-1.05 (2H);¹³C NMR (100 MHz, CDCl₃) δ 175.4, 172.9, 172.6, 172.0, 171.2, 170.5,156.7, 143.6, 141.2, 136.3, 129.2, 129.0, 128.7, 127.8, 127.1, 127.0,125.0, 120.0, 112.3, 81.7, 77.3, 67.2, 60.4, 55.5, 53.0. 52.3, 51.2,47.0, 41.2, 37.0, 36.7, 34.1, 30.0, 29.0, 28.0, 24.9, 24.3, 21.3, 20.9,18.3, 12.0; HRMS (ESI), calculated for C₅₈H₇₄N₈O₁₃S ([M+Na]⁺):1145.4994, found: 1145.4981.

In a dry 25-mL, two-necked, round-bottomed flask was charged withcoupling reagent (1.5 equiv) in DCM (1 mL/mmol) and treated understirring with DIEA (4.0 equiv) at 0° C. for 5 min. Fmoc-Gly-Arg(Mtr)-OH(4) (149.6 mg, 0.22 mmol) was added at 0° C. for 20 min, and mixed withtripeptide (3-1) (106.8 mg, 0.22 mmol). The ice bath was removed after20 min and the stirring continued at room temperature 10 days. The crudeproduct was dried in vacuo and purified by column chromatography onsilica gel to obtain Fmoc-protected peptide (5).

Yield: 30% (PyBOP); 65% (by MoO₂Cl₂/4-nitrobenzoic anhydride).

Purified by column chromatography (EtOAc/MeOH=9.5:0.5, R_(f)=0.6); ¹HNMR (400 MHz, CDCl₃) δ 7.76 (d, J=8.0, 1H, NH), 7.70 (d, J=8.2, 2H),7.56 (d, J=6.4, 1H), 7.51 (d, J=7.2, 2H), 7.42 (bd, 1H, NH), 7.38 (d,J=8.0, 2H), 7.36-7.16 (m, 6H), 7.11-7.06 (m, 5H), 6.86 (d, J=7.6 Hz, 1H,NH), 6.50 (s, 1H), 6.38 (bs, 2H), 4.84 (dd, J=14.0, 6.6 Hz, 1H), 4.67(dd, J=13.8, 8.0 Hz, 1H), 4.45-4.27 (m, 3H), 4.20-4.11 (m, 1H),3.90-3.89 (m, 2H), 3.79 (s, 3H, OCH₃), 3.73-3.71 (m, 1H), 3.65 (s, 3H,OCH₃), 3.54-3.46 (m, 1H), 3.43-3.36 (m, 2H), 3.20-3.16 (m, 1H), 3.05(dd, J=14.0, 9.3 Hz, 1H), 2.71 (t, J=8.0 Hz, 1H), 2.71 (m, 1H), 2.67 (s,3H, CH₃), 2.61 (s, 3H, CH₃), 2.10 (s, 3H, CH₃), 2.01-1.79 (m, 6H),1.76-1.51 (m, 8H), 1.50-1.41 (m, 6H), 1.39 (s, 9H, C(CH₃)₃), 1.32-1.02(m, 8H), 0.94-0.82 (m, 2H); HRMS (ESI) calcd for C₅₈H₇₄N₈O₁₃S (M+⁺H):1122.5098; found: 1122.5096.

Similar procedure like the one for [Scheme II] provide the product in72% yield: Purified by column chromatography (EtOAc/MeOH=9.5:0.5,R_(f)=0.4); ¹H NMR (400 MHz, CDCl₃) δ 7.62 (d, J=8.2, 1H, NH), 7.60 (d,J=8.0, 2H), 7.53 (d, J=6.4, 1H), 7.45 (d, J=7.2, 2H), 7.30 (bd, 1H, NH),7.36 (d, J=8.0, 2H), 7.34-7.18 (m, 6H), 7.18-7.10 (m, 5H), 6.74 (d,J=7.6 Hz, 1H, NH), 6.40 (s, 1H), 6.25 (bs, 2H), 4.81 (dd, J=13.8, 6.8Hz, 1H), 4.70 (dd, J=13.8, 8.0 Hz, 1H), 4.52-4.31 (m, 3H), 4.18-4.08 (m,1H), 3.95-3.86 (m, 2H), 3.77 (s, 3H, OCH₃), 3.73-3.71 (m, 1H), 3.62 (s,3H, OCH₃), 3.68-3.60 (m, 2H), 3.57-3.46 (m, 1H), 3.48-3.36 (m, 2H),3.18-3.12 (m, 1H), 3.08 (t, J=8.0 Hz, 1H), 2.71 (dd, J=14.0, 9.3 Hz,1H), 2.73-2.67 (m, 1H), 2.63 (s, 3H, CH₃), 2.55 (s, 3H, CH₃), 2.11 (s,3H, CH₃), 2.11-1.83 (m, 6H), 1.76-1.61 (m, 8H), 1.55-1.45 (m, 6H), 1.36(s, 9H, C(CH₃)₃), 1.36-1.06 (m, 8H), 0.92-0.84 (m, 2H); HRMS (ESI) calcdfor C₆₂H₈₂N₉O₁₅S (M+⁺H): 1224.5646; found: 1224.5662.

Example 4

After Fmoc, MTR, and t-Boc deprotection:

¹H NMR (400 MHz, CDCl₃) δ 10.02 (bs, 2H, G-NH₂ ⁺), 8.25 (bs, 1H, G-NH),7.83 (bd, J=8.2, 1H, amide NH), 7.75 (d, J=8.0, 1H, amide NH), 7.71 (d,J=8.4, 1H, amide NH), 7.62 (t, J=8.0, 1H, amide NH), 7.36 (d, J=8.2, 1H,amide NH), 7.22-7.11 (m, 5H, Ph), 4.72 (dd, J=15.8, 7.8, 1H), 4.55 (bt,1H), 4.36 (bs, 2H), 4.20 (dd, J=16.0, 7.2, 1H), 3.36 (t, J=14.8 Hz, 2H),3.25-3.12 (m, 4H), 2.64 (dd, J=7.6, 16.0 Hz, 1H), 2.57 (dd, J=16.0,10.4, 1H), 1.84-1.72 (m, 4H), 1.58-1.50 (m, 4H), 1.48-1.38 (in, 4H);HRMS (ESI) calcd for C₂₈H₄₁N₈O₇ (M⁺+H): 601.3098; found: 601.3094; HPLCanalysis: (C18, 250×4.6 mm, 0.5 (mL/min), λ=254 nm). a.1% TFA in H₂O/ACN(95:5) 30 min; b.1% TFA in H₂O/ACN (5:95) 31-60 min; t_(R) 36.71, 46.17min.

A solution of 40.5 mg (0.036 mmol) of the Fmoc-protected peptide (5) wastreated with 20% piperidine in DCM (1 mL) for 1 hour at roomtemperature. After removal of piperidine by coevaporation with methanol,the crude product was dried in vacuo and purified by columnchromatography on silica gel. The resulting product was subjected tointramolecular amide bond formation by treatment with 10 mol % VOOCl₂V(O)(acac)₂, or Ti(O)(acac)₂ in refluxed toluene for 18 h. The resultingcrude mixture was cooled to ambient temperature and concentrated. Thecrude residue was dissolved in trifluoroacetic acid (5 mL) and H₂O (1mL) and then treated with thioanisole (1 mL) The mixture was inducedprecipitation with di-isopropyl ether (5 mL) and the solid washed withdi-isopropyl ether and dried in vacuo to obtain the cyclopeptide (6).The cyclic pentapeptide can be further purified by HPLC on a reversephase C-18 column (gradient: 95/5 to 80/20, H₂O/CH₃CN) to give 18 mg(69% yield) of pure 6.

Before MTr and t-Boc deprotection:

¹H NMR (400 MHz, CDCl₃) δ 7.68-7.287 (m, 1H, imine), 7.22-7.12 (in, 5H,Ph group), 6.50 (s, 1H, amide), 6.33 (br, 2H, amide), 4.80 (dd, J=6.0,6.9 Hz, 1H), 4.59-4.55 (m, 1H), 4.45-4.36 (m, 1H), 3.80 (s, 3H,OCH₃-Ph), 3.33-3.15 (m, 3H), 2.79 (t, J=8.4 Hz, 1H), 2.65 (s, 3H,CH₃-Ph), 2.59 (s, 3H, CH₃-Ph), 2.31 (t, J=10.4 Hz, 1H), 2.08 (s, 3H,CH₃-Ph), 2.03-1.95 (m, 4H), 1.64-1.41 (m, 5H), 1.36 (s, 9H, tBu),1.30-1.27 (m, 2H), 1.25-1.22 (m, 4H); R_(f) 0.5 (EtOAc/MeOH, 9/1); HRMS(ESI) calcd for C₄₂H₆₀N₈O₁₀S (M⁺+H): 868.4153; found: 869.4233.

After Deprotection:

¹H NMR (400 MHz, CDCl₃) δ 10.12 (bs, 2H, G-NH₂+), 8.22 (bs, 1H, G-NH),7.79 (bd, J=8.4, 1H, amide NH), 7.72 (d, J=8.2, 1H, amide NH), 7.68 (d,J=8.2, 1H, amide NH), 7.58 (t, J=8.0, 1H, amide NH), 7.41 (d, J=8.2, 1H,amide NH), 7.24-7.13 (m, 5H, Ph), 4.68 (dd, J=13.2, 6.8, 1H), 4.45 (bt,1H), 4.30 (bs, 2H), 4.22 (dd, J=16.0, 7.2, 1H), 3.30 (t, J=14.0 Hz, 2H),3.18-3.00 (m, 4H), 2.68 (dd, J=7.6, 16.0 Hz, 1H), 2.55 (dd, J=16.0,10.4, 1H), 1.78-1.01 (in, 10H); HRMS (ESI) calcd for C₂₈H₄₁N₈O₇ (M⁺+H):601.3098; found: 601.3090; HPLC analysis: (C18, 250×4.6 mm, 0.5(mL/min), λ=254 nm). a.1% TFA in H₂O/ACN (90:10) 30 min; b.1% TFA inH₂O/ACN (10:90) 31-60 min; t_(R) 34.6, 42.6 min.

Scheme III′-2

After Fmoc, MTR, and t-Boc Deprotection:

¹H NMR (400 MHz, CDCl₃) δ 9.68 (bs, 2H, G-NH₂ ⁺), 8.09 (bs, 1H, G-NH),7.68 (bd, J=8.4, 1H, amide NH), 7.64 (d, J=8.2, 1H, amide NH), 7.60 (d,J=8.2, 1H, amide NH), 7.50 (t, J=8.0, 1H, amide NH), 7.45 (d, J=8.2, 1H,amide NH), 7.27-7.16 (m, 5H, Ph), 4.65 (dd, J=15.8, 7.6, 1H), 4.72 (bt,1H), 4.27 (bs, 2H), 4.15 (dd, J=15.8, 7.4, 1H), 3.32 (t, J=15.2 Hz, 2H),3.24-3.15 (m, 4H), 2.80-2.65 (m, 4H), 2.64 (dd, J=7.6, 16.0 Hz, 1H),2.58 (dd, J=16.0, 10.4, 1H), 2.14-2.06 (m, 2H), 2.05 (bs, 1H, NH),1.89-1.82 (m, 2H), 1.78-1.72 (m, 4H), 1.67-1.48 (m, 2H); HRMS (ESI)calcd for C₂₇H₄₀N₉O₇ (M⁺+H): 601.2972; found: 601.2970; HPLC analysis:(C18, 250×4.6 mm, 0.5 (mL/min), λ=254 nm). a.1% TFA in H₂O/ACN (90:10)20 min; b.1% TFA in H₂O/ACN (5:95) 31-60 min; t_(R) 41.8, 50.4 min.

Although the present invention has been explained in relation to itspreferred embodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the invention as hereinafter claimed.

What is claimed is:
 1. A method for preparing a cyclopeptide, comprisingthe following steps: (A) providing a compound represented by formulas(I′-1) and (II-2):

wherein, Ra is alkyl, cycloalkyl, aryl, or heteroaryl; R_(c) is aprotection group; and R₁ is

in which each of R₂ and R₃ independently is H or C₁₋₆ alkyl; X is O, S,CH₂ or N—R₄, in which R₄ is H, C₁₋₆ alkyl, (CH₂CH₂O)_(n)H, —C(═O)—C₁₋₁₀alkyl, or C(═O)(C₂H₄)₂C(═O)O(C₂H₄O)_(n)H, in which n=1-3; (B) performinga reaction between the compounds of formula (II′-1) and (II-2), toobtain a compound represented by the following formula (II′-3):

(C) performing a reaction between the compound of formula (II′-3) and acompound represented by the following formula (II′-4):

to obtain a compound represented by the following formula (II′-5):

wherein each Rd and Re is a protection group: (D) performing acyclization reaction of the compound of formula (II′-5) with a catalystof formula (III);

wherein M is a metal selected from the group consisting of IVB, VB, VIBand actinide groups; L¹ and L² respectively is a ligand; m and y areintegers of greater than or equal to 1; and Z is an integer of greaterthan or equal to zero; to obtain a compound represented by the followingformula (I′):

and thereby produce a compound represented by any one of the followingformulas (I′-1) to (I′-4):